xfs: always log timestamp updates in xfs_setattr_size

Get rid of the special case where we use unlogged timestamp updates for
a truncate to the current inode size, and just call xfs_setattr_nonsize
for it to treat it like a utimes calls.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>